1. Field of the Invention
The present invention relates to a communication device disposed in a connectionless network as a node and a bandwidth management method for setting a bandwidth to be applied to transmission in the communication device.
2. Description of the Related Art
In recent years, many private networks laid among lodgments of business organizations via public networks and leased lines for realizing transmission of various information related to the organizations' business employ technology of packet switching and frame relay (cell relay) and so on so that they are configured as connectionless networks allowing communication channels to be formed among desired lodgments.
Furthermore, at present, telecommunication carriers have been switching to connectionless networks to which IP (Internet Protocol), Eathernet, and so on having high line utilization efficiency and providing the maximum merits of multiplexing are applied, and as a result, business organizations as their users have also been configuring their networks utilizing more economical services such as low-charged IP-VPN (L3VPN) and L2VPN.
In such a connectionless network, bandwidths to be allotted for transmitting transmission information among individual lodgments are released when there is no transmission information. Therefore, when a large volume of packets are transmitted in parallel to a specific lodgment from a plurality of lodgments, for example, an edge network connected to this connectionless network gets into congestion and many of the packets are likely to be discarded.
Generally, these discarded packets can be restored by a retransmission procedure included in TCP (Transmission Control Protocol), which is an upper ranked transmission protocol of IP.
However, none of the discarded packets, which are transmitted by a communication device terminating a network by a layer above an IP layer or to be received by such a communication device (for example, communication signals and speech signals transmitted/received under UDP (User Datagram Protocol) fall under this category), are restored.
Conventionally, as a prior art for solving the above problem in such a connectionless network, there exists an ATM cell rate/bandwidth controlling system as described, for example, in Japanese Patent Laid-open No. Hei 10-107802, wherein shaping of each transmission information according to bandwidths physically allotted to individual communication devices and a contracted bandwidth of a communication device corresponding to a destination of the transmission information to be transmitted makes it possible to configure almost the same network as a conventional private network in which logical lines are formed between individual destinations and a leased line is utilized.
In the above-described conventional example, bandwidths of paths to be formed among all the lodgments and bandwidths which individual lodgments can allot to transmission according to the combinations of these bandwidths are set manually when necessary.
However, for example, when a bandwidth allotted to a specific lodgment is changed, or when some lodgment is expanded or relocated, previously set bandwidths and so on have to be updated synchronously in all the lodgments.
Moreover, such updating operations cannot be started until the operations of communication devices installed in individual lodgments are forcibly interrupted or until the state and the time permitting the interruption of their operations are recognized.
However, as for networks used, for example, by banks and securities companies and provided for their basic business, the degeneration of transmission quality or the decline in reliability due to the operation interruption of their communication devices at the time of updating bandwidths and so on as described above as well as the aforesaid discarding of packets is not permitted.
Therefore, transmission carriers providing services such as L3VPN and L2VPN (including ‘system integration enterprises’ providing L3VPN and L2VPN services and a device for realizing these services as a system) have strongly demanded that a connectionless network having flexible adaptability to maintenance and operation states and an efficient transmission ability of various transmission information including speech signals be realized.